[core] Compile-time detection of loop() overrides

Replace the runtime GCC-specific pointer-to-member-function comparison
in has_overridden_loop() with a compile-time std::is_same_v check in a
templated register_component_().

The template resolves &T::loop vs &Component::loop at compile time and
passes the result to register_component_impl_(), which stores it as
bit 5 in the existing component_state_ byte (zero additional RAM).

This eliminates:
- The non-standard -Wpmf-conversions GCC extension
- The USE_HOST/CLANG_TIDY special case that incorrectly returned true
  for all components (putting every component in the loop list)
- Runtime vtable probing during calculate_looping_components_()

esphome/core/application.cpp

@@ -79,7 +79,12 @@ static void insertion_sort_by_priority(Iterator first, Iterator last) {
   }
 }
 
-void Application::register_component_(Component *comp) { this->components_.push_back(comp); }
+void Application::register_component_impl_(Component *comp, bool has_loop) {
+  if (has_loop) {
+    comp->component_state_ |= COMPONENT_HAS_LOOP;
+  }
+  this->components_.push_back(comp);
+}
 void Application::setup() {
   ESP_LOGI(TAG, "Running through setup()");
   ESP_LOGV(TAG, "Sorting components by setup priority");

esphome/core/application.h

@@ -5,6 +5,7 @@
 #include <limits>
 #include <span>
 #include <string>
+#include <type_traits>
 #include <vector>
 #include "esphome/core/component.h"
 #include "esphome/core/defines.h"
@@ -531,7 +532,14 @@ class Application {
 #endif
 #endif
 
-  void register_component_(Component *comp);
+  /// Register a component, detecting loop() override at compile time.
+  /// The template resolves &T::loop vs &Component::loop as a constexpr bool
+  /// and forwards it to register_component_impl_ which stores it in component_state_.
+  template<typename T> void register_component_(T *comp) {
+    this->register_component_impl_(comp, !std::is_same_v<decltype(&T::loop), decltype(&Component::loop)>);
+  }
+
+  void register_component_impl_(Component *comp, bool has_loop);
 
   void calculate_looping_components_();
   void add_looping_components_by_state_(bool match_loop_done);

esphome/core/component.cpp

@@ -490,18 +490,6 @@ void Component::set_setup_priority(float priority) {
 }
 #endif
 
-bool Component::has_overridden_loop() const {
-#if defined(USE_HOST) || defined(CLANG_TIDY)
-  return true;
-#else
-#pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Wpmf-conversions"
-  bool loop_overridden = (void *) (this->*(&Component::loop)) != (void *) (&Component::loop);
-#pragma GCC diagnostic pop
-  return loop_overridden;
-#endif
-}
-
 PollingComponent::PollingComponent(uint32_t update_interval) : update_interval_(update_interval) {}
 
 void PollingComponent::call_setup() {

esphome/core/component.h

@@ -76,6 +76,8 @@ inline constexpr uint8_t STATUS_LED_MASK = 0x18;
 inline constexpr uint8_t STATUS_LED_OK = 0x00;
 inline constexpr uint8_t STATUS_LED_WARNING = 0x08;
 inline constexpr uint8_t STATUS_LED_ERROR = 0x10;
+// Component loop override flag uses bit 5 (set at registration time)
+inline constexpr uint8_t COMPONENT_HAS_LOOP = 0x20;
 
 // Remove before 2026.8.0
 enum class RetryResult { DONE, RETRY };
@@ -271,7 +273,7 @@ class Component {
    */
   void status_momentary_error(const char *name, uint32_t length = 5000);
 
-  bool has_overridden_loop() const;
+  bool has_overridden_loop() const { return (this->component_state_ & COMPONENT_HAS_LOOP) != 0; }
 
   /** Set where this component was loaded from for some debug messages.
    *
@@ -510,7 +512,8 @@ class Component {
   /// Bits 0-2: Component state (0x00=CONSTRUCTION, 0x01=SETUP, 0x02=LOOP, 0x03=FAILED, 0x04=LOOP_DONE)
   /// Bit 3: STATUS_LED_WARNING
   /// Bit 4: STATUS_LED_ERROR
-  /// Bits 5-7: Unused - reserved for future expansion
+  /// Bit 5: Has overridden loop() (set at registration time)
+  /// Bits 6-7: Unused - reserved for future expansion
   uint8_t component_state_{0x00};
   volatile bool pending_enable_loop_{false};  ///< ISR-safe flag for enable_loop_soon_any_context
 };